bc: rename zbc_parse_string->bc_parse_pushSTR, do not emit next opcode in it

bc: rename zbc_parse_string->bc_parse_pushSTR, do not emit next opcode in it

function                                             old     new   delta
bc_parse_pushSTR                                       -      73     +73
zbc_parse_stmt_possibly_auto                        1638    1640      +2
zbc_parse_string                                      89       -     -89
------------------------------------------------------------------------------
(add/remove: 1/1 grow/shrink: 1/0 up/down: 75/-89)            Total: -14 bytes
   text	   data	    bss	    dec	    hex	filename
 981377	    485	   7296	 989158	  f17e6	busybox_old
 981363	    485	   7296	 989144	  f17d8	busybox_unstripped

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>